We’re building an A/B testing setup for two Cognigy.AI models. The plan is to route inbound webhooks through a Node.js load balancer that splits traffic based on cookie headers and logs performance metrics to a time-series database. The routing logic looks fine locally, but once it hits the production endpoint, half the payloads just vanish. No 500s, nothing in the error logs. Just silent drops.
Here’s the Express middleware handling the split:
app.post('/webhooks/cognigy', async (req, res) => {
const abCookie = req.cookies['ab-test-model'];
const targetModel = abCookie === 'v2' ? 'https://api.cognigy.ai/v2/models/v2' : 'https://api.cognigy.ai/v2/models/v1';
try {
const response = await fetch(targetModel, {
method: 'POST',
headers: { 'Content-Type': 'application/json', 'Authorization': `Bearer ${process.env.COGNIGY_TOKEN}` },
body: JSON.stringify(req.body)
});
await logMetrics(targetModel, response.status);
res.status(202).send('queued');
} catch (err) {
console.error('routing failed', err);
res.status(502).send('proxy error');
}
});
The time-series logging function just hits our internal /api/v2/metrics/ingest endpoint. That part works. The problem is req.cookies comes back empty even when the browser definitely sent ab-test-model=v2. GC’s web messaging SDK attaches it fine on the client side, but Express isn’t picking it up. Switched to cookie-parser middleware and it’s still undefined. The raw header dump shows Cookie: ab-test-model=v2; gc_session=xyz... but req.cookies stays {}.
Also getting intermittent ETIMEDOUT on the fetch call to the Cognigy endpoint when the split hits v1. v2 responds in 120ms flat. v1 hangs until Node kills it. Maybe the webhook listener is rate-limiting based on source IP. Or maybe I’m misconfiguring the keepAlive agent. The metrics payload I’m sending to the DB looks like this:
{
"timestamp": "2024-05-12T14:30:00Z",
"model": "v1",
"latency_ms": 4500,
"status": "timeout"
}
Wondering if Express is stripping the cookie header because of some security middleware we added last sprint. The GC platform docs mention passing custom headers through the guest API, but nothing about how Node handles them on the receiving end. Checked the network tab on the simulator. The cookie is definitely there. Just dies somewhere in the pipeline.
just move the split logic into the Genesys Cloud flow instead of handling it in Node.js. the system already has a random split node that handles A/B routing without cookie parsing. when you rely on external middleware, the webhook timeout kicks in if the server takes more than five seconds to respond. the payload just disappears from the dashboard and you’ll see zero in the webhook success rate. that metric only counts successful HTTP responses, so silent drops show as failures. the business impact is usually a drop in first contact resolution because the conversation falls back to the default path.
try adding a pause node after the webhook call to let the server process the cookie check. also check the retry limit in the flow settings. default is three attempts. if it hits the limit, the conversation drops. here is what the webhook log usually looks like when it times out:
{
"webhookId": "wh-8821",
"responseCode": null,
"durationMs": 5002,
"status": "timeout",
"retryCount":
the log cuts off there in our environment. where do you set the retry limit in the flow builder. is it under the advanced settings tab. also what does the queue wait time show when these drops happen. we’ve noticed the average handle time jumps when the routing fails because agents get stuck on the fallback menu. the dashboard only shows the active conversations, so the lost ones never hit the metrics. can someone explain what the webhook success rate actually measures in this context. the docs just say HTTP 2xx but it doesn’t match our drop rate.
just switch to the architect split node. it tracks the conversion rate directly in the flow analytics. saves you from debugging cookie headers.
app.post('/cognigy-split', express.json({ limit: '5mb' }), (req, res) => {
const targetModel = req.cookies['ab-test'] === 'model-b' ? 'B' : 'A';
res.status(200).json({ routed: targetModel });
queueMicrotask(() => routePayload(targetModel, req.body));
});
Moving the split into the platform actually sidesteps the cookie parsing overhead. You’ll still need to adjust the WEBHOOK_TIMEOUT and RETRY_POLICY on the Genesys side. It’s usually because the default settings are too strict for hybrid setups. Here’s the PATCH payload you’ll need for the routing configuration:
{
"webhookTimeout": "PT10S",
"retryPolicy": "exponential",
"maxRetries": 3
}
Hit /api/v2/routing/webhooks/{webhookId} with that. Make sure your AUTH_SCOPES include routing:webhook:read and routing:webhook:write. The platform handles the A/B split natively now, so you can drop the Express middleware entirely. Just map the SPLIT_NODE to the two separate ENDPOINT_URL values. The dashboard metrics will finally track correctly instead of showing phantom failures. I’ve seen this exact pattern break during morning syncs here in London when the cookie jar gets bloated. Cookie parsing is heavy. Always kills the throughput. The latency just piles up until the gateway drops the packet.